The present invention relates to controlling the flow of fluids and, more particularly, to the valve arrays used to control the flow of well fluids in a subterranean well tool. Still, more particularly, the present invention relates to the method and apparatus for using layers containing micro check valve arrays to control the flow of fluids in subterranean well filters.
Well filters are typically used in subterranean well environments in which it is desired to remove a liquid or gas from the ground, without bringing soil particulates, such as sand or clay, up with the liquid or gas. A well filter generally includes an inner support member, such as a perforated core and a filter body, including a filter medium disposed around the inner support member. In many cases, the well filter will further include an outer protective member, such as a perforated cage or shroud, disposed around the filter body for protecting it from abrasion and impacts. A filter for subterranean use is described in U.S. Pat. No. 6,382,318, which is hereby incorporated herein by reference for all purposes. A downhole screen and method of manufacture is described in U.S. Pat. No. 5,305,468, which is hereby incorporated herein by reference for all purposes. A downhole sand screen with a degradable layer is described in U.S. Pub. No. 2005/0155772, which is hereby incorporated herein by reference for all purposes.
It is desirable to be able to provide a flow path through the screen to provide circulation, while installing the screen in a well. In the past, such circulation has been provided by a washpipe extending through the screen. The washpipe permits fluid to be circulated through the screen before, during and after the screen is conveyed into the well, without allowing debris, mud, etc. to clog the screen. However, using a washpipe requires additional operations when completing the well for production of hydrocarbons.
Expandable and nonexpandable screens have been used in the past, either with or without the use of a washpipe. When a washpipe is not used, there is no sealed fluid path through the screen to allow fluids to be pumped from the top of the screen to the bottom. As a result, any attempt to circulate fluid in the well would result in large volumes of fluid being pumped through the screen media, potentially plugging or clogging the screen and potentially damaging the surrounding hydrocarbon bearing formation.
Degradable materials have been used and proposed in the past to completed block flow through the screen. These prior systems involve materials that dissolve or degrade over time when placed in the well. However, while the blocking materials degrade these systems prevent production from the well during degradation.
Accordingly, there is a need for improved methods and apparatus to permit circulation through an expandable well screen during its installation in a well, while not requiring additional well operations associated with use of a washpipe and which allow production to begin immediately, once treating fluid circulation ceases. Other benefits could also be provided by improved methods and systems for installing well screens in a well.